Interconnecting substation electrical components with heavy-duty cable conductors requires effective physical flexibility to withstand moderate seismic shaking without damage.
This invention relates to facilitating integrity of electrical interconnection of substation electrical components. In particular, the invention is directed to minimizing problems affecting power utilities operating in seismologically active areas. The invention is directed to substantially reducing earthquake damage to substation equipment.
In substations, high voltage (500 KV and 220 KV class) cable conductors are used to interconnect substation switching equipment. There is a need for adequate flexibility through bending of the conductors to minimize interaction or linking of this equipment during seismic shaking. Without the ability of the conductors to be flexible, brittle equipment components, such as insulators, are subject to breakage from induced loads due to structurally non-compatible interaction with adjacent equipment. The cable conductors are axially stiff and provide the link mechanism which allows axial or longitudinal forces along the cable length to develop and load equipment. Accordingly, linked response forces (LRF) due to movement or resistance to movement of one piece of switching equipment is readily transmitted to an adjacent piece of equipment through the interconnecting stiff cable.
The present manner of minimizing the development of LRF is to introduce a degree of sag into the cable(s) interconnected between adjacent electrical equipments. Increased sag yields increased flexibility. Sag, however, is limited by required electrical clearances between conductors, between conductors and equipment support structures and between conductors and the ground. These electrical clearance requirements have resulted in reduced conductor insulation sag to such an extent that adequate flexibility is not provided by the sag. Without adequate conductor flexibility, cable interconnected adjacent equipment will experience LRF due to seismic shaking. This results in costly failed components and interruption of service.
It is an object of the present invention to provide for increases in conductor flexibility and to maintain integrity between interconnected electrical components during seismic shaking conditions while in normal conditions, the conductor cables will not have excessive sag.